[ITP] cross-pkg-config

[Yaakov (Cygwin/X)]

In cygport git master, I changed how cygport uses pkg-config when 
cross-compiling.

While pkg-config isn't technically a target tool (its configure doesn't 
accept --target), using the plain pkg-config for cross-compiling 
requires setting several environment variables.  While this is easy 
within the confines of cygport, it's not practical for independent usage.

Instead, pkg-config can be configured at build time with several options 
to behave like a target tool by default, and PKG_FIND_PKG_CONFIG 
actually uses AC_PATH_TOOL to find PKG_CONFIG.  Hence, Fedora provides 
such packages for the mingw-w64 toolchains, as do I for my Cygwin 
toolchains there.

Therefore, as of commit af8971d, cygport now requires a $host-pkg-config 
for cross-toolchains.  These packages should be built with 
toolchain.cygclass and configured as such:

>   --disable-host-tool
>   --program-prefix=${TOOLCHAIN_TARGET}-
>   --with-pc-path=${TOOLCHAIN_LIBDIR}/pkgconfig:${TOOLCHAIN_DATADIR}/pkgconfig:/usr/share/pkgconfig
>   --with-system-include-path=${TOOLCHAIN_INCLUDEDIR}
>   --with-system-library-path=${TOOLCHAIN_LIBDIR}

I already have packages for the cygwin and mingw-w64 cross-toolchains. 
I intend to upload these in the next few days, after which I should be 
ready to ship a new version of cygport.


Yaakov